The present invention relates to ovens for closed system operation and, in particular, an oven providing for combined convention and steam cooking and catalytic treatment of cooking fumes.
Commercial ovens, when cooking food, produce cooking fumes and odors that are typically handled by exhaust hoods providing power ventilation of fumes and odors out of the building. In some circumstances, where an exhaust hood is impractical or undesirable, it is known to treat such cooking fumes using catalytic converters which break down the components of the cooking fumes in a catalytic chemical process.
Catalytic converters for this purpose must normally operate at temperatures in excess of 500 degrees Fahrenheit. In some cases, these high temperatures may be provided by the oven heating elements themselves positioned near the catalytic unit for direct heating of the catalytic converter substrates. In such cases, and with convection ovens, the convection fan may force the same heated air used in the cooking process through the catalytic unit to clean this air of cooking fumes.
The high temperatures necessary for practical catalytic converter operation are not compatible with many low temperature cooking processes that nevertheless produce cooking fumes that need processing. In these cases, it is known to provide a chimney holding a catalytic converter and supplemental heaters to heat the catalytic converter and/or the exhaust gases to reduce the cooking fumes prior to venting the hot exhaust gases in a chimney. Chimney venting eliminates the problem of the heated gases unduly raising the internal oven temperature.
Closed-system ovens such as “combination ovens”, cooking with a combination of forced air convection and steam, normally seal the cooking volume to retain heat and moisture and provide energy savings. Many foods that are preferentially made with combination ovens are cooked at temperatures below that necessary to sustain the catalytic action of the catalytic converter and yet nevertheless at temperatures that produce significant cooking fumes and odor. The use of a vent-mounted catalytic converter would defeat the desired sealed environment of the combination oven.